JPH0394993A - Tube material made of aluminum alloy and production thereof - Google Patents

Abstract

PURPOSE:To provide the tube of a highly corrosion resistance at a low cost by using a specifically composed Al alloy as a core material, cladding a brazing material on one surface thereof and an Al material for the sacrificial anode of the inside surface on the other surface to form a combined sheet for tube and forming a chemical conversion treatment film on the clad material side surface for the sacrificial anode of the inside surface. CONSTITUTION:The Al alloy contg., by weight%, 0.2 to 1.5% Mn, <=1% Si, <=0.2% Mg, and, if necessary, at least one kind among <=0.5% Cu, <=0.3% Cr and <=0.2% Zr is used as the core material. The brazing material consisting of an Al-Si system is clad on one surface of the core material. A pure Al or the Al alloy contg. <=2% Zn is clad as the sacrificial anode of the inside surface on the opposite surface, by which the Al alloy-composite sheet material for the tube material to be assembled by brazing is constituted. The chemical conversion treatment film is formed on the surface of the clad material for the sacrificial anode of the inside surface. The excellent corrosion resistance is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tube material for a radiator or the like having high corrosion resistance and a method for manufacturing the same, and is expected to be particularly effective when assembled by the Nocolock brazing method.

(Prior Art and Problems to Be Solved) As a tube material for brazed radiators, plating sheets have been used that have a core material of Al-Mn alloy 3003 or the like and a cladding material of Al-Si brazing material. Ta.

In addition, in order to suppress corrosion from the cooling water side of the radiator tube material, AQ-Zn alloy 7 is applied to the cooling water side.
Composite materials clad with 072 have also been used.

However, even with a composite material in which the cooling water side is clad with Al-Zn alloy 7072, Zn is lost due to heating during brazing.
The anticorrosion effect decreases due to the diffusion of ions, and depending on the conditions of use, corrosion resistance may not be sufficient.

Therefore, in order to improve corrosion resistance, chemical treatment is sometimes applied after brazing assembly, but in this case, the purpose is to prevent pitting corrosion itself, and as a result, a defect-free film is created. required. Therefore, the process becomes complicated and the cost increases significantly. In addition, it is difficult to uniformly apply a chemical conversion treatment to the inner surface of a radiator having a complicated shape, so in reality, such means are not often adopted.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, to provide a tube material such as a radiator tube having high corrosion resistance without impairing brazing properties at a low cost, and to provide a method for manufacturing the same. It is something to do.

(Means for Solving the Problems) As mentioned above, conventionally, the corrosion prevention of the inner surface of the radiator tube with a chemical conversion coating was considered to prevent the occurrence of pitting corrosion, so the treatment had to be performed after brazing. It was thought that it would not be effective. Therefore, although chemical conversion treatment has been known to be effective in improving corrosion resistance, the actual situation is that it is rarely carried out because of the large cost increase.

Furthermore, even if chemical conversion treatment is applied to the inner surface of the radiator tube material, most tube materials do not have a sacrificial anode layer, and furthermore, radiator tube materials that have a sacrificial anode layer on the inner surface inhibit the sacrificial anode effect. In some cases, chemical conversion treatment was not performed.

In view of the above circumstances, the present inventor has conducted extensive research into ways to manufacture highly corrosion-resistant radiator tube material at low cost without impeding brazing properties, and has hereby devised the present invention. This is what I did.

That is, the present invention can be used as a core material. Mn: 0.2-1.
5% and Si:1. Contains 0% or less, Mg: 0. 2
% or less, and if necessary, Cu: 0.5% or less,
Cr: 0. Using an aluminum alloy containing at least one of Zr: 3% or less and Zr: 0.2% or less, an Al-Si brazing filler metal is applied to one side of the core material, and pure aluminum or Zn:2 is applied to the other side. In an aluminum alloy composite sheet for tube material that is assembled by brazing and has a structure in which the inner sacrificial anode is clad with an aluminum alloy containing less than The gist of this invention is an aluminum alloy tube material that is characterized by:

In addition, the method for producing the tube material includes forming an aluminum alloy composite material having the above structure into a sheet with the final thickness by a conventional method, performing heat treatment, and then chemically treating only the surface on the side of the inner sacrificial anode cladding material. The method is characterized in that the tube material is obtained by cutting, width cutting, and seam welding to form an electric resistance welded tube.

The present invention will be explained in further detail below.

(Function) As shown in FIG. 1, an aluminum alloy with a specific composition in which Mg contained as an impurity is regulated to 0.2% or less is used as the core material in contact with the Al-Si brazing material.

Further, the surface opposite to the core material (the surface opposite to the brazing material) is clad with pure aluminum or an aluminum alloy containing Zn as a skin material.

In the aluminum alloy composite material made in this way, only on the surface of the cladding material (skin material) for the sacrificial anode,
It has been found that if the sheet (coil) is subjected to chemical conversion treatment, then width trimmed, and seam welding is performed to manufacture an electric resistance welded tube, cost increases can be minimized and the corrosion prevention effect is also excellent.

In applications such as radiator tubes, a cladding layer of pure aluminum or a Zn-containing aluminum alloy protects the core material sacrificially, but the anodic coating applied to this surface increases cathodic polarization. As a result, the rate of disappearance of the cladding layer is suppressed, and alkali corrosion of the core material due to excessive corrosion protection is prevented under all usage environments, resulting in a marked improvement in corrosion resistance.

It is predicted that the chemical conversion coating applied before brazing heating will cause countless defects due to brazing heating, but the purpose of chemical conversion treatment is not to prevent pitting corrosion by the coating, but to improve corrosion resistance by increasing cathodic polarization. Therefore, the formation of film defects due to brazing heating is practically not harmful.

In addition, since the wide coil is chemically treated only on one side, the chemical treatment does not adhere to the brazing metal surface and impede brazing performance.

Next, the reasons for limiting the chemical components in the present invention will be explained.

Core material: The allowable amount of Mg as an impurity contained in the core material before brazing is limited to 0.2% or less in order to prevent deterioration of brazability. This is preferable because it causes a decrease in brazing performance when brazing by the Nocolok method.

By adding Mn to the core material, corrosion resistance, brazing properties, and strength can be improved. However, the amount of Mn added is 0.2
If the content is less than 1.5%, the effect will be insufficient, and if the content exceeds 1.5%, macrocompounds will be generated and processability will be deteriorated, which is not preferable.

Similarly, Cu: 0. 5% or less, Cr: 0.
3% or less, Zr: 0. Addition up to 2% improves corrosion resistance,
Although brazing properties and strength can be improved, if the upper limit is exceeded, the effect is saturated and workability decreases, which is not preferable. However, these Cu. Cr and Zr are added as necessary.

Also, adding Sj to the core material improves the strength, but ↓. If it exceeds 0%, the melting point of the core material will decrease, which is not preferable.

Skin material: Pure aluminum or Zn-containing aluminum alloy is used as the skin material clad on the cooling water side. Regarding the Zn content in the Zn-containing aluminum alloy, it is sufficient that the Zn content can protect the core material as a sacrificial anode after brazing. Although it varies depending on the application conditions, etc., it is within the range of 2.0% or less. If the Zg content exceeds 2.0%, wear of the cladding layer increases, which is not preferable.

Brazing material: An Al-Si alloy is used as the brazing material, but its composition is not particularly limited. For example, 4004
, 4045, etc.

Note that the thicknesses of the core material, skin material, and brazing material can be determined as appropriate.

The chemical conversion treatment applied to the surface of the sacrificial anode alloy cladding material of the aluminum alloy composite sheet having the above structure forms a protective film on the surface of the aluminum alloy and is stable at the brazing temperature. For example, although not particularly limited, coating-type phosphoric acid chromate or silicate treatment is preferable since one side is subjected to chemical conversion treatment.

The best time to perform the chemical conversion treatment is after the final rolling and after the tempering treatment, since a wide range of conditions can be achieved at the lowest cost and it is easy to prevent the formation of a chemical conversion film on the surface of the brazing material.

Next, examples of the present invention will be shown.

(Example) An aluminum alloy (partly containing pure aluminum) having the chemical properties shown in the construction table was prepared. In the same table, Nn 1 ・
~Na 5 is the core material, Na 1 1 ~ Na 1
4 is the skin material cladding on the cooling water side, Nα20 ~
Na21 is the brazing material.

By combining these, materials (sheets) for radiator tube materials shown in Table 2 were manufactured. In addition, in the same table, Nα
40 is the case where no skin material is provided.

Next, a chemical conversion treatment was applied to only the surface of the skin material facing the cooling water side of the tube material material under the conditions shown in Table 3 to obtain a test material. Table 4 shows the combinations of tube materials and annealing treatments. For comparison, a tube material that was subjected to chemical conversion treatment after heating for brazing was also produced.

Apply 5g/m of Franks for Nocolock to the brazing material surface of the tube material shown in Table 4, and after drying,
It was heated at 600° C. for 5 minutes in a N2 gas atmosphere. Note that only N058 was subjected to heating equivalent to vacuum brazing.

Test Example 1 The corrosion resistance of the skin material side clad on the cooling water side of the tube material material after heating was investigated.
:300ppm. So4: 100ppm.
Cu: 5 ppm) at 88°C for 8 hours at room temperature
An immersion test was conducted for 30 days under different temperature conditions, and the hole depth was measured and evaluated. The results are also listed in Table 4. The brazing performance was evaluated by measuring the flow coefficient when brazing was performed under the brazing conditions described above. The results are shown in Table 4, and even if chemical conversion treatment is applied before brazing,
No decrease in brazing properties was observed.

Table 4 also lists the results of tensile tests conducted on each tube material.

Combining the above test results, all of the examples of the present invention:
It has excellent corrosion resistance without sacrificing brazability, and can be manufactured at low cost.

On the other hand, the comparative examples have poor corrosion resistance, or even if they have good corrosion resistance (NG63 to N064, Nα68), they are not practical due to the bulky manufacturing cost.

[Blank below] (Effects of the Invention) As detailed above, according to the present invention, in the material for tube materials such as radiators, a composite material is made of aluminum materials of a specific composition and combination, and the sheet (coil) ) (i.e., before manufacturing the ERW pipe and before heating it for brazing), the chemical conversion treatment is applied only to the surface of the skin material, so it has excellent erodibility, and it also allows the chemical conversion treatment to be applied after brazing. Manufacturing costs can be significantly lower than in the conventional case. Therefore, highly corrosion-resistant radiator tube material can be obtained at low cost, and when used in automobile heat exchangers, etc., it has significant effects such as thinner walls, lighter weight, and cost reductions. Particularly remarkable effects are exhibited when assembled by the saw-brazing method. It goes without saying that the present invention is not limited to tube materials for radiators, but can be applied to anything having the same structure as a radiator, such as a heater core.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the cross-sectional structure of the aluminum alloy tube material of the present invention.

Claims (3)

[Claims] (1) In weight% (the same applies hereinafter), as a core material, Mn:
0.2 to 1.5% and Si: 1.0% or less, Mg
: Regulated to 0.2% or less, and further Cu: 0.5 as necessary.
% or less, Cr: 0.3% or less, and Zr: 0.2% or less, one side of the core material is clad with an Al-Si brazing filler metal, and the other side is clad with an Al-Si brazing filler metal. In an aluminum alloy composite sheet for a tube material assembled by brazing, the cladding material side for the inner sacrificial anode has a structure in which pure aluminum or an aluminum alloy containing 2% or less of Zn is clad for the inner sacrificial anode. An aluminum alloy tube material with a chemical conversion coating formed on its surface. (2) The tube material according to claim 1, wherein the chemical conversion coating is phosphoric acid chromate-based or silicate-based. (3) The aluminum alloy composite material having the structure according to claim 1 is made into a sheet with the final thickness by a conventional method, and after being subjected to heat treatment, a chemical conversion treatment is applied only to the surface on the side of the inner sacrificial anode cladding material, 1. A method for manufacturing an aluminum alloy tube material, the method comprising: cutting the width, and seam welding the tube material into an electric resistance welded tube.